The Britain-based Syrian Observatory for Human Rights said warplanes bombed neighbourhoods around the capital including the rebel stronghold of Douma.

Damascus-based activist Maath al-Shami said government troops are firing rockets and mortars at orchards near the southern suburbs of Daraya and Kfar Sousseh.

The Observatory, meanwhile, said troops are fighting rebels in Aqraba and Beit Saham, also south of Damascus, near the city's international airport.

It also reported air raids, clashes and shelling around other parts of the country.

The UN said on Wednesday that more than 60,000 people have been killed since Syria's crisis began in March 2011 - a figure much higher than previous opposition estimates.

Earlier, the president of the UN Security Council said important developments were under way in efforts to find a diplomatic solution to the 21-month war and there could be another US-Russia meeting with international envoy Lakhdar Brahimi next week.

Pakistan's UN ambassador Masood Khan told a news conference that Mr Brahimi was trying to pave the way for a diplomatic breakthrough and planned to follow up talks in Moscow last Saturday with Russian foreign minister Sergey Lavrov with new three-way talks.

Mr Brahimi and Mr Lavrov both said after their meeting that the Syrian conflict could be settled only through talks, while admitting that the government and the opposition had shown no desire for compromise. Neither hinted at a possible solution that would persuade the two sides to agree to a ceasefire and sit down for talks about a political transition.

Mr Lavrov said Syrian president Bashar Assad had no intention of stepping down - a key opposition demand - and it would be impossible to try to persuade him otherwise.